Organic light-emitting diode (OLED) is a hot area in the current development of flat panel display devices. Compared with liquid crystal display (LCD) devices, OLED display devices typically have advantages such as low power consumption, low manufacturing cost, self-luminescence, wide viewing angle, and fast response speed. At present time, OLED display devices are starting to replace traditional LCD display devices, such as in cell phones, tablet computers, digital cameras, large-screen TVs, etc.
Unlike an LCD, which employs a stable voltage to control its brightness, an OLED is driven by an electric current, and a stable current is needed for the control of light emission. For reasons related to manufacturing processes and component aging, the threshold voltage (Vth) of driver transistors of the pixel circuit is not constant, causing changes in the current flowing through each OLED, which in turn results in non-uniform brightness of display, negatively influencing the whole image display effect.
In addition, the current flowing through each OLED is related to the voltage of the source electrode of the associated driver transistor, i.e., the voltage of the power supply. A voltage drop across the circuits resulting from the product of the electrical current (I) and the resistance (R), referred to as the IR Drop, can also result in differences in currents in different areas of the screen, in turn causing non-uniform brightness in OLEDs in different areas.